During the pickling, etching, chemical shaping etc. of steels, stainless steels, special alloys and special metals and the dissolution of those metals, metalliferous solutions of the acids employed arise in the course of such processes which must either be disposed of by neutralization or be used for the recovery of the acids and metals by expensive processes. According to the invention the production or recovery of nitric acid or a mixture of nitric acid and hydrofluoric acid takes place by spray-roasting the solutions at temperatures of 200° to 500° in a reactor (1) and subsequent absorptions or condensation of the gases generated in column means (7, 8) at temperatures of 0° to 70° C.

Process for the production or recovery of acids from metalliferous solutions of such acids

A process for substantially reducing the amount of insoluble fluoride-forming species in a coal feed material comprising slurrying a coal feed with a fluoride acid in the presence of an amount of fluoride-complexing species at least equal to the amount necessary to form tightly-bound complex ions with substantially all free-fluoride-ions in the slurry to produce a leached coal product and a spent leach liquor, and separating the leached coal product from the spent leach liquor. The process produces a clean purified fuel with ash content of less than about 5%, and preferably less than about 1%. Loss of fluorine values by formation of insoluble fluorides is minimized. Alkali metals and alkaline earths are substantially dissolved. The process generally comprises sizing the coal to 10 mm or less, leaching the sized coal with hydrofluoric acid in the presence of a determinable amount of a fluoride-complexing species such as silicon or aluminum, separating the leached coal from the spent leach liquor, and optionally some or all of the following: (a) pre-drying or physically beneficiating feed with high moisture or high mineral matter (ash) content; (b) cleaning the leached coal by washing and/or (c) heat treatment; (d) freeing pyrite (and other heavy minerals) and coal from attached silicates and aluminosilicates and physically separating the freed pyrite; (e) subjecting the leached coal to a second strong acid leach. In the preferred processes, hydrofluoric acid is recovered for recycling.

Process for producing a clean hydrocarbon fuel from high calcium coal

Regeneration of a spent process soln. (I) contg. HF acid and metal fluorides and/or metal oxides comprises: (i) passing (I) into a reactor, where it is subjected to pyrohydrolysis at 200-1000 deg C; (ii) completely recovering the metals as mixed oxide; (iii) removing dust from the reactor waste gas contg. HF and cooling to 60-100 deg C; and (iv) the removing HF by scrubbing with water in an absorber and discharging the resultant recovered HF acid.

Regeneration of spent hydrofluoric acid esp. pickling acid

A process for treating mixtures of solid coal and fly ash containing metallic oxides, silicon dioxide and sulfur compounds in order to produce treated coal and substantially pure silicon dioxide comprising (1) reacting a mixture of the coal and fly ash with hydrogen fluoride in water to produce a liquid stream comprising silicon fluoride and metal fluorides and a solids stream comprising unreacted coal and sulfur compounds; (2) reacting the sulfur compounds with metallic nitrates dissolved in water to form an aqueous solution of nitrate, metallic and sulfur ions; (3) separating the aqueous solution of nitrate, sulfur and metallic ions from the solid coal; (4) washing the previously treated solid coal with water; (5) reacting the silicon fluorides and metal fluorides with metallic nitrates in an aqueous mixture to form solid silicon dioxide; and separating the solid silicon dioxide from the aqueous mixture.

Process for obtaining treated coal and silica from coal containing fly ash

A method and system for treating coal with hydrogen fluoride to remove fly ash and thereafter regenerating substantially all of the hydrogen fluoride used during the process (thereby significantly reducing the amount of HF on site). An exemplary method includes the steps of charging at least one reaction vessel with coal containing fly ash; feeding hydrogen fluoride into the reaction vessel to form a first reaction mixture of soluble reaction products, insoluble fluoride compounds and initially clean coal; separating out the first soluble and insoluble reaction products; feeding nitric acid into the same reaction vessel to react with any remaining fly ash components and separating out those second reaction products; and regenerating substantially all of the hydrogen fluoride used in the first fluoride reaction.

Ash removal from coal: process to avoid large quantities of hydrogen fluoride on-site

A method of obtaining or recovering hydrofluoric acid from metal fluorides and solutions containing such, e.g. pickling solutions. In this procedure heavy metal fluorides are brought into contact with water vapor at 200° C. to 800° C., with an overall pressure of about 1 bar keeping the vapor partial pressure in a sufficiently linear relationship with the temperature in this range at a minimum of 0.9 bar at 400° C. and at a minimum of 0.5 bar at 600° C., separating the solid reaction material from the gaseous phase while still hot and obtaining aqueous hydrofluoric acid from the latter by--preferably indirect--cooling.

Krepler Albert

Papers

Method and an installation for obtaining or recovering hydrofluoric acid

Verfahren und anlage zur gewinnung bzw. rueckgewinnung von flussaeure